An organic positive temperature coefficient thermistor device comprises a resistive element (thermistor body) in which conductive particles are dispersed in a polymer organic compound, and a pair of opposing electrodes disposed so as to hold the resistive element therebetween. A current is caused to flow between the pair of electrodes, whereby the thermistor device is utilized as an overcurrent/overheating protector device, a self-regulated heater, or a temperature sensor.
Organic positive temperature coefficient thermistor devices have been required to exhibit characteristics of a low room-temperature resistance value, a high resistance change ratio, and a high reliability in resistance value reproducibility or the like. As organic positive temperature coefficient thermistor devices responding to such a request, those using a crystalline polymer as a polymer organic compound are disclosed in U.S. Pat. Nos. 3,243,753 and 3,351,882. Also, an organic positive temperature coefficient thermistor device using a heat-curable resin is disclosed in U.S. Pat. No. 4,966,729.
Further, organic positive temperature coefficient thermistor devices using a conductive particle having spiky projections as a conductive particle are disclosed in Japanese Patent Application Laid-Open Nos. 5-198403 and 5-198404. Also, an organic positive temperature coefficient thermistor device using conductive short fibers is disclosed in Japanese Patent Application Laid-Open No. 5-198404.
Further, Japanese Patent Application Laid-Open No. HEI 5-198404 states that using a metal powder having spiky projections or flaky metal powder as a conductive particle and mixing therewith a low molecular alcohol or amine having at least three functional groups as a polymer organic compound can yield a low room-temperature resistance value and a large resistance change ratio. It further discloses that an organic positive temperature coefficient thermistor devices having such a high resistance value reproducibility that the change in room-temperature resistance value is small after heating and cooling is obtained.
As electronic devices have recently been becoming smaller, organic positive temperature coefficient thermistor devices have further been required to reduce their sizes. The organic positive temperature coefficient thermistor devices have been made smaller mainly by reducing their dimensions in electrode surface directions, i.e., by decreasing their electrode area.